CSI Codebook Spatial Basis Selection With Shared Co-Phase
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Solution Overview
Problem
Existing wireless communication systems face challenges in reducing signaling overhead and UE complexity when selecting spatial domain bases for multi-layer precoding matrices, particularly in channel state information codebooks, due to the need for independent co-phase selection and reuse of bases across layers, which increases inter-layer interference.
Innovation Solution
The proposed solution involves selecting a first spatial domain basis for a layer from a codebook and additional bases from a subset orthogonal to the first basis, using a common or shared co-phase coefficient to ensure orthogonality, thereby reducing the need for independent co-phase selection across layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If independent co-phase selection is performed for each layer, then orthogonality between spatial domain bases is ensured, but signaling overhead and UE complexity increase
Solution Approach 1:
The patent merges the co-phase selection process across multiple layers by introducing a common co-phase coefficient that applies to all layers simultaneously. Instead of independently selecting co-phases for each layer, the system uses a single common co-phase coefficient, thereby reducing UE complexity and signaling overhead while maintaining orthogonality between spatial domain bases through the shared selection mechanism.
2Device complexity
If spatial domain bases are reused across layers, then signaling overhead is reduced, but inter-layer interference increases
Solution Approach 1:
The patent applies local quality by constraining the selection of spatial domain bases for each layer based on the previously selected basis. Specifically, for the second layer, only spatial domain bases orthogonal to the first layer's basis are allowed, creating a localized constraint that prevents reuse of the same basis across layers while maintaining overall system efficiency. This constrained selection mechanism reduces inter-layer interference.
3Object-generated harmful factors
If constrained selection of spatial domain bases is performed, then inter-layer interference is reduced, but the number of available bases decreases
Solution Approach 1:
The patent introduces a new dimension to the base selection process by incorporating co-phase coefficients as an additional degree of freedom. Instead of solely relying on spatial domain basis orthogonality, the system uses the combination of constrained basis selection and co-phase modulation to achieve interference reduction. This dimensional expansion allows the system to maintain versatility while preventing inter-layer interference through the joint optimization of basis selection and co-phase parameters.
Data Source
AI summary
Various aspects of the present disclosure generally relate to reducing overhead and/or user equipment (UE) complexity when performing independent spatial domain (SD) basis selection in a channel state information (CSI) codebook. For example, a UE may select any SD basis in a codebook for a first layer, and may SD bases selected for additional layers may be restricted to SD bases that are orthogonal to the first SD basis. Furthermore, SD bases that are selected for a layer may be excluded from SD basis selections for subsequent layers, ensuring that different SD bases are selected for each layer. Accordingly, because SD basis selections for multiple layers are not reused and guaranteed to be orthogonal, a common or shared co-phase coefficient may be used for each SD basis selection to reduce a per-layer co-phase reporting overhead and/or UE complexity by avoiding a need to independently select co-phases for multiple layers.